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MUNGBEAN
PRODUCTION GUIDE
CAMBODIA
ACIAR MONOGRAPH 214
2 MUNGBEAN PRODUCTION GUIDE I CAMBODIA
MUNGBEAN
PRODUCTION GUIDE
CAMBODIA
2020
The Australian Centre for International Agricultural
Research (ACIAR) was established in June 1982 by an Act
of the Australian Parliament. ACIAR operates as part of
Australia’s international development assistance program,
with a mission to achieve more productive and sustainable
agricultural systems, for the benefit of developing
countries and Australia. It commissions collaborative
research between Australian and international researchers
in areas where Australia has special research competence.
It also administers Australia’s contribution to the
International Agricultural Research Centres.
The Chief Executive Officer of ACIAR reports directly to the
Australian Government Minister for Foreign Affairs. ACIAR
operates solely on budget appropriation from Australia’s
Official Development Assistance (ODA).
Where trade names are used this constitutes neither
endorsement of nor discrimination against any product
by ACIAR.
ACIAR MONOGRAPH SERIES
This series contains the results of original
research supported by ACIAR, or material deemed
relevant to ACIAR research and development
objectives. Publications in the series are available
as hard copy, in limited numbers, and online from
the ACIAR website at aciar.gov.au
© Australian Centre for International Agricultural
Research (ACIAR) 2020
This work is copyright. Apart from any use as permitted
under the Copyright Act 1968, no part may be reproduced
by any process without prior written permission from
ACIAR, GPO Box 1571, Canberra ACT 2601, Australia,
aciar@aciar.gov.au
Martin, R. Montgomery, S. Yous, S & Rien, R. 2020,
Mungbean production guide for Cambodian conditions,
ACIAR Monograph No. 214, Australian Centre for
International Agricultural Research, Canberra. 76 pp.
ACIAR Monograph No. 214 (MN214)
ISSN 1031–8194 (print)
ISSN 1447–090X (PDF)
ISBN 978-1-922345-77-6 (print)
ISBN 978-1-922345-78-3 (PDF)
Technical editing by Coretext
Design by WhiteFox.com.au
Printing by Elect Printing
Cover: After cassava, maize and soybean, mungbean was
the fourth most important non-rice crop in Cambodia
in 2016. Mungbean will flower for as long as there is
sufficient soil moisture and a single plant can have flowers,
green pods and black pods all present at the same time.
Photos: R. Martin and S. Yous
FOREWORD
Mungbean presents smallholder farmers in Cambodia with an opportunity to diversify
crop production in traditional rice production systems. The crop has a number of
agronomic benefits and meets growing global demand for beans for sprouting,
cooking and processing.
Cambodia’s National Strategic Development Plan 2019–2023 is the road map for
the implementation of the Rectangular Strategy Phase IV. A key element of the
Rectangular Strategy is stepping up diversification and productivity in the agriculture
sector, which remains a challenge to be addressed in terms of poverty reduction
and improvement in livelihoods. According to the Ministry of Agriculture, Forestry
and Fisheries, production of mungbean and other rice-diversification crops has
been increasing in recent years. This is consistent with priority having been given
to diversifying and intensifying sustainable agricultural production, with low inputs,
and to developing cost-effective management practices.
The Australian Centre for International Agricultural Research (ACIAR) was mandated,
as set out in the Australian Centre for International Agricultural Research Act 1982, to
work with partners across the Indo-Pacific region to generate the knowledge and
technologies that underpin improvements in agricultural productivity, sustainability
and food systems resilience. We do this by funding, brokering and managing research
partnerships for the benefit of partner countries and Australia.
This guide is based on knowledge and outputs of ACIAR-supported mungbean
research carried out in Cambodia over 18 years. Information is drawn from the
following projects:
> ‘Farming systems research for crop diversification in Cambodia and Australia’
(ASEM/2000/109), 2003–07
> ‘Enhancing production and marketing of maize and soybean in north-western
Cambodia and production of summer crops in north-eastern Australia’
(ASEM/2006/130), 2007–12
> ‘Market-focused integrated crop and livestock enterprises for north-western
Cambodia’ (ASEM/2010/049), 2012–16
> ‘Sustainable intensification and diversification in the lowland rice system in
north-west Cambodia’ (CSE/2015/044), 2016–21.
MUNGBEAN PRODUCTION GUIDE I CAMBODIA iii
This publication supersedes Mungbean production guide for Cambodian conditions (ACIAR Monograph No. 162), published in 2016. Notably, significant progress has been made in satisfying growers’ criteria for a mungbean variety with combined attributes of large shiny seeds and resistance to pod shattering. The Cambodian mungbean variety CMB-2 currently best satisfies the grower criteria and will go into commercial production in 2021. The integrated pest management (IPM) schedule for managing mungbean insect pests has been fine-tuned to include biological insecticides and sticky traps that have made it possible to eliminate the use of synthetic insecticides in mungbean. The projects listed above have made a significant contribution to capacity building for Cambodian provincial staff from the Ministry of Agriculture, Forestry and Fisheries, universities, non-governmental organisations and the private sector, for the implementation of new technologies and improved practices in mungbean production systems. This book is part of a series of publications produced by ACIAR that support of the ongoing roll-out of more productive, economic and environmentally sustainable and diversified cropping systems in Cambodia. Andrew Campbell Chief Executive Officer, ACIAR iv MUNGBEAN PRODUCTION GUIDE I CAMBODIA
CONTENTS
FOREWORD iii
Acknowledgments vi
Authors vi
Abbreviations vii
Tables viii
Figures ix
MUNGBEAN IN CAMBODIA 1
Mungbean production in Cambodia 2
Growing season 3
Constraints to production 4
Effects of straw mulch on mungbean yield in rice fields 5
Opportunities for mungbean in Cambodia 6
CROP PRODUCTION 7
Soil and water management 8
Land preparation and planting 12
Crop establishment 13
Options to improve profitability of mungbean 18
Mungbean growth stages 20
Harvesting and desiccation 25
WEED MANAGEMENT 26
DISEASES 28
INSECT PESTS 32
BENEFICIAL INSECTS 47
INTEGRATED PEST MANAGEMENT FOR MUNGBEAN 53
Integrated pest management 55
IPM strategy for managing mungbean insect pests 57
Insect identification mobile phone application for mungbean 58
GRAIN STORAGE PESTS 60
Seed storage options 63
REFERENCES 64
v
ACKNOWLEDGMENTS This manual is an updated version of ACIAR Monograph No. 162, providing new and additional information. The information in this manual is based on research by the Cambodian Agricultural Research and Development Institute (CARDI), University of Battambang (UBB), and the Provincial Departments of Agriculture, Forestry and Fisheries (PDAFF) in Battambang, Kampong Cham and Pailin. The research was supported by the New South Wales Department of Primary Industries, the University of New England and the University of Sydney. We also thank the World Vegetable Center (Dr Srinivasan Ramasamy for identification and management of insect pests in mungbean and Dr Abhay Pandey for identification and management of diseases of mungbean). This research was funded by the Australian Centre for International Agricultural Research (ACIAR) in the projects: > ASEM/2000/109 (2003–07) > ASEM/2006/130 (2008–11) > ASEM/2010/049 (2012–16) > CSE/2015/044 (2016–21). AUTHORS Robert Martin, Agricultural Consultant, Battambang, Cambodia Stephanie Montgomery, Northern Ag Focus Pty Ltd, Wagga Wagga NSW, Australia Sophea Yous, University of Battambang, Battambang, Cambodia Ratha Rien, University of Battambang, Battambang, Cambodia vi MUNGBEAN PRODUCTION GUIDE I CAMBODIA
ABBREVIATIONS
2,4-D 2,4-dichlorophenoxyacetic acid
ACIAR Australian Centre for International Agricultural Research
app application
AVRDC Asian Vegetable Research and Development Center
CARDI Cambodian Agricultural Research and Development Institute
CMB Cambodian mungbean
Fe iron
GRDC Grains Research and Development Corporation
GVB green vegetable bug
ha hectare
IPM integrated pest management
K potassium
kg kilogram
m 2
square metre
MAFF Ministry of Agriculture, Forestry and Fisheries
ML megalitre
mL millilitre
mm millimetre
MYMV mungbean yellow mosaic virus
N nitrogen
NCDD National Committee for Sub-National Democratic Development
P phosphorus
PDAFF Provincial Departments of Agriculture, Forestry and Fisheries
PPE personal protective equipment
S sulfur
SC soluble concentrate
SL soluble liquid
SUT Suranaree University of Technology, Thailand
t tonne
UBB University of Battambang
WVC World Vegetable Center
Zn zinc
MUNGBEAN PRODUCTION GUIDE I CAMBODIA vii
TABLES
Table 1. Cambodia crop production statistics for 2016 (MAFF 2017). 2
Table 2. Actual and achievable mungbean yields in Battambang province (kg/ha). 4
Table 3. Options for increasing mungbean yields. 6
Table 4. Effect of seed size and target plant population on choice of seeding rate (kg/ha). 14
Table 5. Gross margin comparison for current practice (for a yield of 1 t/ha)
vs improved practice (for a yield of 1.5 t/ha) at $1/kg. 19
Table 6. Effect of varying yield and price for improved practice mungbean gross margin. 19
Table 7. Vegetative growth stages for mungbean after Pookpakdi et al. (1992). 22
Table 8. Reproductive growth stages for mungbean after Pookpakdi et al. (1992). 22
Table 9 Herbicides that can be used in mungbean in Cambodia. 27
viii MUNGBEAN PRODUCTION GUIDE I CAMBODIAFIGURES
Figure 1. Mungbean growing season windows for lowland and upland. 3
Figure 2. Suspected potassium deficiency. 9
Figure 3. Nodulaid® Group I root nodule bacteria inoculum for cowpea and mungbean,
Suranaree University of Technology liquid inoculum for mungbean. 10
Figure 4. Rhizobium root nodules and healthy nodules cut open to show pink flesh. 10
Figure 5. Machine harvesting of rice can leave a no-till seedbed. 12
Figure 6. Rice residues can be mulched to keep weed seeds on the soil surface. 12
Figure 7. Planting mungbean. 12
Figure 8. Dry-season mungbean machine planted into rice residue at 60 cm row spacing. 13
Figure 9. Pod shattering is a problem for DX-208 variety. 15
Figure 10. Cambodian mungbean (CMB)-2 has large seeds. 15
Figure 11. Evaluation of mungbean varieties for Cambodian conditions. 16
Figure 12. Pod shattering at 62 days after sowing. 17
Figure 13. 100-seed weights of mungbean varieties. 17
Figure 14. Mungbean seedling morphology. 20
Figure 15. Growth stage VE. 21
Figure 16. Growth stage VC. 21
Figure 17. Growth stage V1. 21
Figure 18. Growth stage V2. 21
Figure 19. Mungbean flowers. 23
Figure 20. The rice field rat. 24
Figure 21. Combine harvesting mungbeans in Aek Phnum district. 25
Figure 22. Mungbean yellow mosaic virus (MYMV) symptoms on mungbean leaf. 29
Figure 23. Cercospora leaf spot on mungbean. 29
Figure 24. Halo blight. 30
Figure 25. Powdery mildew. 31
Figure 26. Bean fly pupae and adult. 33
MUNGBEAN PRODUCTION GUIDE I CAMBODIA ixFigure 27. Twenty-eight spotted ladybird adult and larva. 34 Figure 28. Cluster caterpillar adult and larva. 35 Figure 29. Legume web spinner: adult Omiodes indicata and O. diemenalis; and Omiodes larva. 36 Figure 30. Maruca podborer adult and larva. 37 Figure 31. Pea blue and gram blue butterfly adults and larvae. 38 Figure 32. Bean flower thrip adults. 39 Figure 33. Whitefly. 40 Figure 34. Cowpea aphids clustered on flowers and in close up on a stalk. 41 Figure 35. Mealybugs in a cluster and a single mealybug. 42 Figure 36. Helicoverpa podborer adult and larva. 43 Figure 37. Green vegetable bug adult and 3rd instar nymphs. 44 Figure 38. Red-banded shield bug adult and nymph. 45 Figure 39. Brown bean bug adult and nymph. 46 Figure 40. Six-spotted ladybird adult, larva and pupa. 49 Figure 41. Transverse ladybird adult, larva and pupae. 50 Figure 42. Adult Trichopoda and a small white egg on a Nezara viridula adult. 51 Figure 43. Trissolcus basalis adult ovipositing into GVB eggs. 52 Figure 44. Using beat sheet and sweep net to check on insect populations in soybean. 55 Figure 45. Example of IPM in mungbean. 56 Figure 46. Blue sticky traps for control of flower thrips. 57 Figure 47. Good vs bad ladybirds. 58 Figure 48. Screenshots of the Pest ID app. 59 Figure 49. Cowpea bruchid adult and bruchid eggs on mungbean seed. 61 Figure 50. Rice weevils. 62 Figure 51. Lesser grain borers. 62 Figure 52. GrainPro™ seed storage bags. 63 x MUNGBEAN PRODUCTION GUIDE I CAMBODIA
MUNGBEAN IN CAMBODIA
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 1Mungbean production in Cambodia Mungbean (Vigna radiata (L.) R. Wilczek) is a short-duration legume crop. In Cambodia, it begins flowering after approximately 30 days and produces mature pods from 60 to 90 days after sowing. Mungbean plants are branching, erect and self-pollinating and have a rooting depth of 60–100 centimetres (cm). Mungbean are grown to supply a human consumption market, so management for high seed quality is essential. The area of agricultural production in Cambodia was 4.04 million hectares (ha) in 2016 of which rice was 3.12 million ha (77%) (Table 1). After cassava, maize and soybean, mungbean was the fourth most important non-rice crop in Cambodia with an area of 37,598 ha, or less than 1% of the total cropped area, in 2016. With 5,172 ha, Battambang province accounted for 14% of the mungbean area in Cambodia with an average yield of 900 kilograms per hectare (kg/ha) in 2016 (MAFF 2017). Table 1. Cambodia crop production statistics for 2016 (MAFF 2017). Crop Area sown (ha) Area harvested (ha) Production (t) Yield (t/ha) Rice total 3,118,160 3,099,769 9,952,270 3.21 Rice wet season 2,599,586 2,581,255 7,626,906 2.95 Rice dry season 518,574 518,514 2,315,364 4.47 Cassava 651,862 642,918 14,175,497 22.05 Maize 115,719 112,699 542,288 4.81 Soybean 41,611 41,606 69,406 1.67 Mungbean 37,598 36,587 49,815 1.36 Vegetables 27,310 27,308 238,082 8.72 Sugar cane 17,484 17,484 613,352 35.08 Sesame 14,683 14,603 13,730 0.94 Peanut 12,484 12,484 19,105 1.53 Sweet potato 3,417 3,417 24,472 7.16 2 MUNGBEAN PRODUCTION GUIDE I CAMBODIA
MUNGBEAN IN CAMBODIA
Growing season
250 37
36
200
35
Tmax (°C)
Rainfall (mm)
150
34
33
100
32
50
31
0 30
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Lowland
Upland
Figure 1. Mungbean growing season windows for lowland and upland. The orange line is average
monthly maximum temperature and the blue line is average monthly rainfall. For
planting suitability: green = yes; yellow = maybe; orange = no.
In Cambodia, mungbean can be grown in the upland and lowland. In lowland rice
systems, mungbean is commonly grown as an opportunity crop in the early dry
season between November and February depending on residual soil water after the
main wet-season rice crop or after receding floodwaters. In upland cropping systems,
mungbean is commonly grown in the early wet season between March and July
(Figure 1). However, the risk of crop failure of February–April plantings in the upland is
very high at 59%, whereas the failure risk isConstraints to production The average yield of mungbean in lowland districts is 819 kg/ha (Table 2; NCDD 2010) but farmers claim they can achieve 1,500 kg/ha. If true, this would give a potential exploitable yield gap of 681 kg/ha for lowland crops (Stuart et al. 2016). Soils are more fertile in the upland and the average yield is 1,119 kg/ha. This compares to an easily achievable yield of 2,000 kg/ha, giving an exploitable yield gap of 881 kg/ha in the upland. However, yields of up to 3,000 kg/ha have been achieved in experimental fields in the upland. In both systems it is estimated that farmers are achieving only 50–60% of obtainable yield. Table 2. Actual and achievable mungbean yields in Battambang province (kg/ha). System Actual Achievable Gap Per cent Upland 1,119 2,000 881 56% Lowland 819 1,500 681 55% 4 MUNGBEAN PRODUCTION GUIDE I CAMBODIA
MUNGBEAN IN CAMBODIA Effects of straw mulch on mungbean yield in rice fields Results from a study by Som et al. (2011) In rice-based lowland areas, the lack of full irrigation water availability for post-rice legume crops and the poor physical and chemical conditions of the soil are major constraints for developing a sound rice–legume double-cropping system. Options to improve legume productivity include using rice straw mulch and various crop establishment methods. A study by Som et al. (2011) found that mulching of rice straw at 1.5 tonnes per hectare (t/ha) increased mungbean crop establishment from 72% to 83%, reduced weed biomass from 164 to 123 kg/ha and increased yield from 228 to 332 kg/ha. Crop residue mulching was effective in conserving soil moisture, and at crop maturity the mulched area had on average 1% higher soil moisture content. Varying the amount of mulch between 1 and 2 t/ha did not show consistent effects, partly because some mulch treatments resulted in excessive soil moisture content and were not effective for increasing yield. Rice straw mulch had a significant effect on mungbean yield, and mean yield increase with mulch was 35%. This yield advantage was attributed to better crop establishment, improved vegetative growth and reduced weed pressure, but in some cases only one or two of these factors were effective. On the other hand, planting method, tillage method and planting density had only small effects on mungbean yield in most experiments. Only in one location out of four tested did the no-till treatment produce significantly higher yield than the conventional method (Som et al. 2011). Machine seed drill produced similar mungbean establishment and grain yield to hand planting, suggesting that the planter can be used to save the labour cost, which is increasing rapidly. Maximum root depth varied little with mulch or plant-density treatments, and was shallow (
Opportunities for mungbean in Cambodia
Although the average yield for mungbean in Cambodia is only about 1 t/ha, with
reasonable improved practice, farmers should be able to get yields of at least 1.5 t/ha.
At a price of 3,000 riel/kg ($750/t), this would return a gross margin of $625/ha.1
Mungbean is one of the most profitable crops farmers can grow in rotation with
rice. Options for increasing mungbean yields have been identified through farmer
consultation and benchmarking farmers’ fields (Table 3).
Table 3. Options for increasing mungbean yields.
Problem Current practice Improved practice
Pod shattering Limited choice of varieties Varieties with desired attributes
Lack of soil Two passes of a disc plough, hand Crop residue retention, minimum or no
water broadcasting, harrowing after seeding tillage, drill planting
Poor crop No basal fertiliser, foliar fertiliser Basal NPK + trace elements fertiliser +
nutrition application rhizobial inoculation
Poor weed Post-emergence herbicide on Pre-emergence herbicide is more
control stressed weeds timely and effective
Insect pests Broad-spectrum insecticides applied Seed dressing with systemic insecticide
in vegetative stage cause flaring of + integrated pest management (IPM)
secondary pests (e.g. thrips, aphids, giving priority to managing pests
mealybugs) attacking pods
Diseases Application of fungicide Resistant varieties, seed treatment
Suspected Limited use of foliar fertilisers to Test strips of potassium chloride (KCl)
potassium (K) promote flowering in farmers’ fields
deficiency
1 All dollar amounts are in US$.
6 MUNGBEAN PRODUCTION GUIDE I CAMBODIACROP PRODUCTION
Key management tips
> Select soil that drains freely.
> Use high-quality seed, and check the germination percentage, disease status
and varietal purity of seed.
> Fertilise according to soil test analyses, yield potential and field history.
> Inoculate seed using Nodulaid® Group I peat inoculant or liquid inoculant
from Suranaree University of Technology (SUT), Thailand.
> Calculate the required seeding rate to achieve a plant establishment of
20–30 plants.
> Select row spacing to fit the farming system: wide rows offer more flexibility in
sowing, and weed and insect management; narrow rows offer higher potential
yields and greater weed competition under ideal soil water conditions.
> Assess potential weed problems and carefully plan weed control tactics
(options to effectively control broadleaf weeds are limited).
> Begin insect monitoring from the late vegetative (bud initiation) stage
(28–35 days after planting) to ensure timely and effective control decisions.
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 7Soil and water management For machine harvesting, fields selected for mungbean should be fairly uniform in soil type and crop residue cover, and free from harvest impediments such as tree stumps and rocks. These are important considerations because of the low height of mungbean pods and to reduce the tendency for uneven crop maturity. Field history Mungbean is best included in the rotation after a cereal crop, such as maize in the upland or rice in the lowland. Because mungbean is sensitive to several residual herbicides, care needs to be taken when selecting fields where residual herbicides have been used on the previous crop or fallow. Soil management Mungbean prefers well-drained soils with a medium to heavy texture. It does not grow well where there is soil compaction or waterlogging. In the upland, Ferrosols (Labanseak) and Vertosols (Kampong Siem) are ideal for growing mungbean (White et al. 1997). Some rice soils, such as Toul Samrong (hard-setting heavy clays), are not suitable for planting mungbean. Rice soils typically have a hard pan at 15–20 cm (Figure 2), and mungbean roots generally do not grow below this layer. Therefore, mungbeans planted after rice will require access to supplementary irrigation on some soil types. The surface of Toul Samrong soil becomes extremely hard and cracks as it dries out. Reference should be made to White et al. (1997) when choosing lowland soil types for mungbean planting. Mungbean is well suited to no-till situations. Planting into standing maize or rice stubble should result in taller plants with pods higher above the ground, which makes machine harvesting easier. No-till also increases the preservation of residual soil moisture after the main wet-season crop and reduces the risk of crop failure. 8 MUNGBEAN PRODUCTION GUIDE I CAMBODIA
CROP PRODUCTION
Nutrition
Mungbean grow best on fertile, sandy loam soils with good internal drainage and a pH
above 6.0. Except for Kampong Siem soil group, most Cambodian cropping soils are
below this pH. Root growth can be restricted on heavy clays. Mungbean can show iron
chlorotic symptoms and certain micronutrient deficiencies on more alkaline soils such as
some soils in the Kampong Siem group.
Fertiliser recommendations are best based on soil test results, yield potential and field
history. When properly inoculated and planted into situations with low background soil
nitrogen levels, mungbean should fix sufficient nitrogen to support their own growth.
Mungbean often leave some residual nitrogen for the following crop.
Basal fertiliser should contain mainly phosphorus (P) and potassium (K) and as little
nitrogen (N) as possible. Mungbean should not require fertiliser topdressing. Basal
application of di-ammonium phosphate (25 kg/ha) and muriate of potash (25 kg/ha) is
recommended, but can be varied depending on soil fertility and yield potential. Because
Cambodian soils vary widely in pH and natural fertility, adding trace elements is a
precautionary measure.
Mungbean crops in Aek Phnum district, Battambang province, display symptoms of
potassium deficiency (Figure 2), but this has yet to be confirmed.
Figure 2. Suspected potassium deficiency. Photo: R. Martin
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 9Rhizobial inoculants
Mungbean should be inoculated with a Group I inoculant such as Nodulaid® (Figure 3).
Seed should be sown into moist soil as soon as possible after inoculation to increase
the survival of the rhizobia. Inoculation may be carried out by two alternative methods:
coating the seed with a peat slurry (Nodulaid® product) or coating with a liquid inoculant
(Suranaree University of Technology, Thailand). Nodulation should be checked 30 days
after sowing for sufficient numbers of active pink nodules (Figure 4). Nodulation failure
can lead to a significant yield reduction.
Figure 3. Nodulaid® Group I root nodule bacteria inoculum for cowpea and mungbean
(left), Suranaree University of Technology liquid inoculum for mungbean
(right). Photos: R. Martin
Figure 4. Rhizobium root nodules (left) and healthy nodules cut open to show pink flesh
(right). Photos: R. Martin
10 MUNGBEAN PRODUCTION GUIDE I CAMBODIACROP PRODUCTION
Waterlogging
Mungbean does not tolerate waterlogging, so choice of soil type and irrigation
management are very important. Waterlogging reduces the ability of nodules to
fix nitrogen and also induces nitrogen deficiency. Irrigated mungbean is estimated
to require 3.5–4.5 megalitres per hectare (ML/ha) of water. Where waterlogging is
expected, planting mungbean onto hills or raised beds will allow better drainage.
Suggested timing of irrigation is:
> irrigation 1—about 7 days before the start of flowering, which is usually around
30 days after planting
> irrigation 2—early pod development.
Irrigating too late into the grain-fill phase may cause another flush of flowers to be
produced, causing split maturity in the crop. This will delay harvest and increase the risk
of loss in quality.
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 11Land preparation and planting
Mungbean can be planted into rice crop residues from mid-November to mid-January,
depending on the rice harvest date and soil moisture content (Figure 5). Earlier sowings
could be affected by late rain and waterlogging. Header trails should be removed before
planting.
Figure 5. Machine harvesting of rice can leave a no-till seedbed.
Photo: R. Martin
Burning rice straw should be avoided because it dries out and hardens the soil surface,
and can reduce establishment options for mungbean after rice.
Figure 6. Rice residues can be mulched Figure 7. Planting mungbean.
to keep weed seeds on the soil Photo: R. Martin
surface. Photo: R. Martin
12 MUNGBEAN PRODUCTION GUIDE I CAMBODIACROP PRODUCTION
Crop establishment
Mungbean is normally hand planted at 40 cm row spacing in Cambodia.
The recommended row spacing for machine-planted mungbean in Cambodia is
30 cm under good soil water conditions. A wider row spacing of 60 cm is
recommended for dry-season sowing when soil water is limited and no irrigation is
available. Narrow rows (30 cm) are recommended on active floodplain alluvial loamy
soils with adequate soil water.
Figure 8. Dry-season mungbean machine planted into rice residue at 60 cm row spacing.
Plant population and sowing depth
The aim should be to establish 20–30 plants per square metre (plants/m2) in non-irrigated
dry-season crops and 30–40 plants/m2 in wet season or irrigated situations. Establishing
a uniform plant density is critical to achieving uniform plant maturity across the field. The
planting depth across the width of sowing machinery should be even to ensure even crop
emergence.
The number of seeds per kilogram of mungbean seed can vary widely—from 10,000
to 20,000 depending on variety and growing conditions. Therefore, it is recommended
that the sowing rate is calculated using germination test results, seed count per kilogram,
the target plant population and establishment percentage. The sowing depth should
be 3–5 cm.
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 13Calculating sowing rates
The following formula can be used to calculate sowing rates, taking into consideration:
> the number of seeds per kilogram (seeds/kg; seed size or seed weight)
> the target plant population
> germination percentage (e.g. 90% germination = 0.9 in the formula)
> establishment rate (usually 80% = 0.8 in the formula, unless sowing in adverse
conditions).
Target plant population/m2 × 10,000
Sowing rate (kg/ha) =
Germination × establishment rate × seeds/kg
Worked example:
25 plants/m2 × 10,000
Sowing rate (kg/ha) = = 28
0.9 × 0.8 × 12,500
Seed size of mungbean grown in Cambodia generally ranges from 11,000 to
14,500 seeds/kg, and the average is between 12,500 and 13,000 seeds/kg. Larger
seeds require higher seeding rates (Table 4). The optimum plant population also varies
according to the availability of soil water; it can be increased if there is adequate soil
water and reduced if soil water is limiting.
Table 4. Effect of seed size and target plant population on choice of seeding rate (kg/ha).
Seeds Target plant population (plants/m2)
(per kg) 15 20 25 30 35
11,500 18 24 30 36 42
12,000 17 23 29 35 41
12,500 17 22 28 33 39
13,000 16 21 27 32 37
13,500 15 21 26 31 36
14,000 15 20 25 30 35
14 MUNGBEAN PRODUCTION GUIDE I CAMBODIACROP PRODUCTION
Seed quality
Seed used for planting should ideally have germination percentages above 90%.
Take care with some varieties as hard (dormant) seed levels may vary. A high percentage
of hard seed can result in uneven germination and establishment. The level of hard
seed (by test) should be kept to a minimum; above 20% hard seed is not advisable in
seed for planting.
Seed kept on-farm for re-sowing can lose quality quickly. Seed quality can be reduced
by seed-borne diseases, damage by grain storage insect pests, and weed seed
contamination. It is recommended that farmers purchase seed with a certification label.
Before purchasing seed, check for damage by grain storage insects (see ‘Grain storage
pests’, below).
Varieties
Apart from high yield, mungbean growers are looking for reduced pod shattering
(Figure 9) and large-seeded varieties (Figure 10).
Figure 9. Pod shattering is a problem for Figure 10. Cambodian mungbean (CMB)-2
DX-208 variety. Photo: S. Chhun has large seeds. Photo: R. Martin
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 15Varietal evaluations 2004–06
Mungbean varieties were evaluated for adaptation to Cambodian conditions over
a range of environments in 2004–06 by the Cambodian Agricultural Research and
Development Institute (CARDI) (Ouk et al. 2009). Genotypes evaluated were from the
Asian Vegetable Research and Development Center (AVRDC—now the World Vegetable
Center), Australia and Thailand. These were compared with local farmer varieties.
Two sets of mungbean varietal evaluation experiments were carried out in Cambodia
between 2004 and 2006 (Ouk et al. 2009). The best-performing varieties were VC
4152 and VC 3541 (AVRDC), and ATF 3944 from Australia (Figure 11). All varieties
outperformed local varieties, and farmers preferred the new varieties. These three
varieties have been released by CARDI as CMB-1 (VC 4152), CMB2 (VC 3541) and
CMB-3 (ATF 3944). Mungbean seed originating from both Thailand and Vietnam can
be purchased at most seed stores. However, quality is inconsistent, and germination
tests should be carried out before large amounts of seed are bought.
a) Group 1
900
850
800
Yield (kg/ha)
750
700
650
600
550
500
NM 94 VC 3960 VC 3891 VC 6381 VC 6368 NM 97 CARDI Chey VC 6220 VC 3541 VC 4152
b) Group 2
900
850
800
Yield (kg/ha)
750
700
650
600
550
500
KK 2 KK 3 ATF 3942 ATF 3941 CARDI Chey VC 4152 VC 2768 ATF 3946 ATF 3944 ATF 3945
Figure 11. Evaluation of mungbean varieties for Cambodian conditions. The orange bars
are CARDI Chey (locally released variety) and the green bars represent the
varieties selected for release.
16 MUNGBEAN PRODUCTION GUIDE I CAMBODIACROP PRODUCTION
Varietal evaluations 2019–20
Mungbean growers in Battambang plant two varieties—DX-208 (Vietnam) and
KPS-2 (Thailand)—and pick twice, around 60 and 90 days after sowing. Under this
regime, pod shattering is a problem with DX-208 but not with KPS-2. However,
DX-208 is preferred for seed size and price.
Although the Cambodian varieties (CMB-1, CMB-2 and CMB-3) were released prior
to 2009, they were still not commercially available in 2020. Varietal testing in 2019
and 2020 has revealed that CMB-2 meets farmer specifications with a low level of
pod shattering comparable to KPS-2 (Figure 12) and large seeds comparable to
DX-208 (Figure 13).
100
pods % pods %
75
100
50
Shattered
75
25
50
Shattered
0
25 KPS-2 CMB-1 CMB-2 CMB-3 CARDI Chey DX-208
0
Figure 12.
8.5 PodKPS-2
shattering atCMB-1
62 days after CMB-2
sowing (%). CMB-3 CARDI Chey DX-208
weight (g)
8
8.5
7.5
weight (g)
8
100-seed100-seed
7
7.5
6.5
7
6.0
CMB-1 KPS-2 CMB-3 CARDI Chey DX-208 CMB-2
6.5
6.0
CMB-1 KPS-2 CMB-3 CARDI Chey DX-208 CMB-2
Figure 13. 100-seed weights of mungbean varieties.
Orange bars represent CMB-2, which best satisfies the farmer requirement for resistance
to pod shattering combined with large seeds.
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 17Options to improve profitability of mungbean Improved practices are designed to reduce input costs and at the same time increase yield of mungbean. Although farmers are attempting to grow low-input mungbean at the end of the wet season, excessive tillage reduces valuable soil moisture and, consequently, lowers yield potential (Table 5). Replacing hand broadcasting with machine drill planting enables tillage operations, as well as seeding rates, to be reduced. The comparison in Table 5 assumes that improved practice increases yield from 1.0 to 1.5 t/ha. Currently, mungbean growers apply up to 10 insecticide treatments throughout the crop cycle regardless of the presence or absence of insect pests. The improved practice alternative is integrated pest management (IPM), whereby insecticides are not applied unless predetermined economic thresholds are exceeded. This can significantly reduce the cost of crop protection without reducing the economic return (Table 5). Farmers can achieve 1 t/ha. Assuming a price of $1/kg, this would provide an income of $1,000/ha and a gross margin of $564/ha with farmer practice. Experimental yields indicate that improved practices could lift mungbean yields to over 2,500 kg/ha and gross margins up to $2,000/ha. Assuming that improved practice can achieve 1.5 t/ha, an on-farm gross margin of over $1,000 is achievable (Table 5). Mungbean is a relatively safe crop to grow after rice with a break-even yield of 0.43 t/ha and a break-even price of $288/t. Commercial yields and prices are well above these thresholds (Table 6). 18 MUNGBEAN PRODUCTION GUIDE I CAMBODIA
CROP PRODUCTION
Table 5. Gross margin comparison for current practice (for a yield of 1 t/ha) vs
improved practice (for a yield of 1.5 t/ha) at $1/kg.
Income
Yield (kg/ha) 1,000 1,500
Price ($/kg) 1 1
Income ($/ha) 1,000 1,500
Variable costs (US$) Current Improved
Operation practice practice
Ploughing (current—twice; improved—once) 60 30
Seeding (current—30 $/ha; improved—24 $/ha) 47 37
Inoculant 0 5
Seed treatment with insecticide 0 5
Seeding method (current—hand broadcast; improved—machine planting) 5 36
Harrowing (current—after broadcasting) 15 0
Herbicide (quizalofop + fomesafen) 18 18
Foliar fertiliser 21 21
Fungicide 13 13
Insect management (current—prescriptive; improved—IPM) 113 52
Hand harvesting 144 217
Total variable costs/ha 436 434
Gross margin per hectare 564 1,068
Table 6. Effect of varying yield and price for improved practice mungbean
gross margin.
Yield Price ($/t)
(t/ha) 800 900 1,000 1,100 1,200
0.75 168 243 318 393 468
1.13 468 580 693 805 918
1.50 768 918 1,068 1,218 1,368
1.88 1,068 1,255 1,443 1,630 1,818
2.25 1,368 1,593 1,818 2,043 2,268
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 19Mungbean growth stages
Mungbean has epigeal emergence—that is, cotyledons appear above the soil surface.
Following cotyledon emergence, a pair of unifoliate leaves begin unfolding. Thereafter,
alternate trifoliate leaves arise from all nodes above the unifoliate node. Mungbean are
branching, erect or sub-erect and usually stand 0.5–1.0 m high when they have finished
vegetative growth.
Unifoliate leaves
Cotyledons
Hypocotyl
Primary root
Figure 14. Mungbean seedling morphology.
20 MUNGBEAN PRODUCTION GUIDE I CAMBODIACROP PRODUCTION
Figure 15. Growth stage VE. Photo: R. Martin Figure 16. Growth stage VC. Photo: R. Martin
Figure 17. Growth stage V1. Photo: R. Martin Figure 18. Growth stage V2. Photo: R. Martin
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 21Table 7. Vegetative growth stages for mungbean after Pookpakdi et al. (1992).
Code Stage Description
VE Emergence Cotyledons near the soil surface with the seedling showing some part of
the plant above the soil surface.
VC Cotyledon Cotyledons separate from each other on the upper surface. Unifoliate
leaves start to unroll so that the edges of the leaves are not touching
each other.
V1 First node Unifoliate leaves attached to the first node are fully expanded and flat
while the 1st trifoliate leaf attached to the upper node begins to unfold.
V2 Second node 1st trifoliate leaf attached to the second node is fully expanded and flat
while the 2nd trifoliate leaf on upper node starts to unfold.
V3 Third node 2nd trifoliate leaf attached to the fourth node is fully expanded and flat
while the 3rd trifoliate leaf on the upper node starts to unfold.
V4 Fourth node 3rd trifoliate leaf attached to the fourth node is fully expanded and flat
while the 4th trifoliate leaf on the upper node starts to unfold.
V(n) Nth node A node is counted when its trifoliate leaf is unfolded and its leaflets are
flat.
Table 8. Reproductive growth stages for mungbean after Pookpakdi et al. (1992).
Code Stage Description
R1 Beginning flower One open flower at any node on the main stem.
R2 Beginning pod One pod of 1.0 cm length between nodes 4 and 6 of the main stem.
R3 Beginning seed One pod of 5.0 cm length found on any of the top three nodes on
the main stem.
R4 Full seed One pod on any of the top three nodes has constriction between
seed.
R5 Start maturity One pod on the main stem turns to brown, dark brown or black.
R6 First harvest Fifty per cent of pods on the plant are mature.
R7 Second harvest R7 is reached after the remaining pods on the plant mature.
22 MUNGBEAN PRODUCTION GUIDE I CAMBODIACROP PRODUCTION
Mungbean are determinate in their growth habit: vegetative growth stops when
flowering commences, meaning that the crop will have reached its final height. However,
mungbean have an indeterminate flowering habit: they do not have a defined flowering
period and will continue to flower for as long as there is sufficient soil moisture. This
means that a single plant can have flowers, green pods and black pods all present at
the same time. The reproductive stages of mungbean are described in Pookpakdi et al.
(1992) (Table 8).
Under Cambodian conditions, mungbean plants progress from emergence to the
beginning of flowering in around 30 days. Flowers are yellow or greenish yellow in
colour (Figure 19) and are normally grouped in clusters of 5–15. If flowers abort, new
flowers will appear if moisture conditions allow. Successive flushes of flowers and pods
will occur while the soil stays wet. Most of the pods form on the top third of the plant.
Each pod contains 10–15 almost-round, green seeds.
Figure 19. Mungbean flowers. Photo: S. Yous
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 23Rats
Figure 20. The rice field rat. Photo: R. Martin
In some districts, including Thmar Kuol and Aek Phnum, some farmers have
stopped growing mungbean in the dry season because they have not been able
to control rats. Rats are very difficult to control. A combination of methods,
such as physical barriers around the perimeter of the field, water moats, traps
and rodenticides, are required for control.
Baiting can be done using the anticoagulant flocoumafen. Suitable bait
locations include active rat holes, along runs and under rubbish. A barrier of
bait locations is established between rat living areas and the crop. Secure three
or four bait blocks at each bait location on wire or nails, or inside rat bait boxes.
Also place one or two in each rat hole. Inspect the bait locations after 3 days,
and select new locations where there has been no rat activity. Inspect again
4 days later and replace any blocks that have been eaten. Repeat the inspection
of all bait locations at 7-day intervals, replacing fresh blocks only when blocks
have been eaten, until all signs of rat activity have disappeared. Normally only
three or four baiting rounds are required.
24 MUNGBEAN PRODUCTION GUIDE I CAMBODIACROP PRODUCTION
Harvesting and desiccation
Figure 21. Combine harvesting mungbeans in Aek Phnum district.
Photo: Reaksa Sao
In Cambodia, mungbean is traditionally harvested by hand. Two or three pickings are
required because of the prolonged duration of flowering; however, this can cost more
than $200/ha. Some farmers in Battambang are now picking once only and finishing
off with a combine harvesting machine (Figure 21). Machine harvesting requires even
maturity across the field, and desiccation may be required to maximise yield and
quality. Glyphosate can be applied as a desiccant when 90% of pods are yellow or black.
Harvesting can commence 8–16 days after herbicide application when the leaves are
dry. Harvest losses can result when mungbean are too dry when harvested, due to both
the increased risk of shattering and moisture weight losses. Mungbean are susceptible
to wet weather at maturity, which causes seed swelling, discolouration, moulds and
cracking. They should therefore be harvested as early as practical.
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 25WEED MANAGEMENT
Descriptions of weeds commonly found in upland mungbean crops in Cambodia can be
found in Weeds of upland crops in Cambodia (Martin and Pol 2010).
Weed management tips
> Include cereal crops (rice, maize) in the rotation.
> Make sure seed for planting is free from weed seeds.
> Control weeds, especially those that reproduce vegetatively, before sowing.
> Use a post-sowing, pre-emergence herbicide as a priority.
> Apply post-emergence herbicides if necessary.
> Prevent weeds from setting seed during the crop cycle and post harvest.
26 MUNGBEAN PRODUCTION GUIDE I CAMBODIAIt is important to control weeds before sowing. This applies especially to weeds that
reproduce from rhizomes, stolons, tubers (such as Cyperus rotundus) or pieces of stem
(such as Cyanotis axillaris). If such species are present, the final cultivation should be
replaced by application of glyphosate + 2,4-D.
Mungbean are generally regarded as being poor competitors with weeds. However,
mungbean planted after rice or flood into the dry season is able to capture soil water
ahead of the weeds. Weed competition reduces water use efficiency, interferes with
harvesting and contaminates the seed sample. Weeds such as Ageratum conyzoides can
also be alternative hosts of diseases such as mungbean yellow mosaic virus (MYMV).
The virus can be transmitted from the weed to mungbean by whitefly (Bemisia tabaci).
Herbicide options for control of broadleaved weeds in mungbean are limited
(Table 9). Emphasis must therefore be on selecting fields that do not have a problem
with broadleaved weeds.
Table 9. Herbicides that can be used in mungbean in Cambodia.
Active Mode of action Pre-plant Post-sowing Post-emergence
ingredient group pre-emergence
2,4-D 4 ✓
Glyphosate 9 ✓
S-metolachlor 15 ✓
Pendimethalin 3 ✓
Imazethapyr 2 ✓
Fomesafen 14 ✓
Clethodim 1 ✓
Quizalofop 1 ✓
Because herbicides are now widely used in Cambodia, herbicide resistance should
be kept in mind when selecting herbicides for use in mungbean. Rotating grass crops
(maize, rice) with mungbean enables rotation of herbicides with different modes of
action (WSSA 2020), which will delay the development of herbicide resistance. However,
herbicides are only part of an integrated weed management strategy to better manage
weeds and reduce the likelihood of the development of herbicide resistance.
Mungbean can be damaged by residues of sulfonylurea herbicides such as metsulfuron
methyl + chlorimuron ethyl or bensulfuron methyl, which are used in rice, or atrazine,
which is used in maize. Under normal conditions, residues should not be a problem, but
mungbean should not be planted as a replacement for failed maize or rice crops when
herbicide residues could still be active in the soil. Residues tend to stay in the soil for
longer under alkaline or dry conditions, but these conditions are unusual for Cambodia,
where most soils are acidic.
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 27DISEASES
Disease management tips
> Include cereal crops (rice, maize) in the rotation.
> Make sure seed for planting is coated with fungicide.
> Prevent damage from insects, birds and rodents, because such damage can
allow pathogens to enter the plant through wounds.
> Avoid stresses to the crop, including water stress and too much fertiliser.
> Control weeds, because weeds are alternative hosts for many diseases.
> Apply fungicide if appropriate.
28 MUNGBEAN PRODUCTION GUIDE I CAMBODIAMungbean yellow mosaic Cercospora leaf spot
virus (Cercospora canescens)
Figure 22. Mungbean yellow mosaic Figure 23. Cercospora leaf spot on mungbean.
virus (MYMV) symptoms on Photo: cropgenebank.sgrp.cgiar.org
mungbean leaf. Photo: R. Martin
Control of the vector Bemisia tabaci is the Cercospora leaf spot (Figure 23), caused
main option for control of mungbean by the fungus Cercospora canescens, is an
yellow mosic virus (MYMV) (Figure 22), but important fungal disease of mungbean
it is important to be sure that the pest in Cambodia. It is most destructive under
is present in the crop before applying humid, tropical conditions. A range of
insecticide. registered fungicides effectively control
this disease, including carbendazim,
Integrated pest management is the best difenconazole, hexaconazole, mancozeb,
approach to maintain populations of propiconazole and thiophanate methyl.
beneficial insects. IPM is also important
to delay or avoid the development of
insecticide resistance in important insect
pests such as B. tabaci.
Weeds that host MYMV, such as Ageratum
conyzoides, should be controlled in and
around the mungbean field. MYMV is
widely touted as a major disease of
mungbean in South-East Asia. It occurs
in mungbean-growing areas in eastern
Cambodia, such as Chamkar Leu district
in Kampong Cham province, but it does
not appear to be a common disease of
mungbean in north-west Cambodia.
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 29Halo blight
(Pseudomonas savastanoi pv. phaseolicola)
Figure 24. Halo blight. Photo: R. Martin
Symptoms appear 7–10 days after P. s. pv. phaseolicola can survive between
infection. Extensive yellow halos crops on alternative hosts, and in infected
surrounding small (1–2 millimetres (mm)) seeds, and to a limited extent on infected
dark, water-soaked (shiny) spots appear plant residues. Infected seed is considered
on younger leaves (Figure 24). On older to be the major mode of survival and
leaves the halo is not apparent. A shiny spread of the pathogen, and one infected
circular lesion develops on infected pods seed in 10,000 can start an outbreak
and a cream-coloured exudate containing under suitable weather conditions.
bacterial cells may ooze from the lesion.
P. s. pv. phaseolicola is spread during
Alternative hosts of P. s. pv. phaseolicola wet, windy weather, with entry through
occurring in Cambodia belong to the stomates or wounds under moist
family Fabaceae and include: Phaseolus conditions (dew, rain or irrigation).
vulgaris, Cajanus cajan, Centrosema spp., Temperatures in the range 18–25 oC are
Desmodium spp., Glycine max, Lablab most conducive for infection and disease.
purpureus, Macroptilium spp., Pueraria spp.
and Vigna unguiculata.
30 MUNGBEAN PRODUCTION GUIDE I CAMBODIADISEASES
Powdery mildew
(Erysiphe polygoni)
Figure 25. Powdery mildew. Photo: R. Martin
Powdery mildew can be a serious disease In the dry season, powdery mildew
of mungbean (Figure 25). It is favoured by is found on lower leaves as the crop
warm, humid conditions. Mungbeans are matures, but does not cause economic
usually planted in the early wet season damage.
(February–March) in the upland and after
flood or the main wet-season rice crop Sulfur-based fungicides provide good
in the lowland (November–December). control of powdery mildew. Carbendazim
Mungbeans are not normally grown in the can also be used to control powdery
main wet season when powdery mildew mildew in mungbean.
could be an economic problem.
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 31INSECT PESTS
Insect management tips
> Keep weeds under control between crop plantings.
> Make sure seed for planting is coated with insecticide.
> Carefully check for pests and beneficial insects before applying insecticide.
> Avoid application of broad-spectrum insecticides in the vegetative stage, to
preserve beneficial arthropods.
> Control weeds in and around the field, because weeds are alternative hosts
for many insects.
> Apply insecticide if crop damage thresholds are exceeded.
Pest and beneficial insects commonly found in upland crops in Cambodia are described
in Insects of upland crops in Cambodia (Pol et al. 2010).
32 MUNGBEAN PRODUCTION GUIDE I CAMBODIABean fly
(Ophiomyia phaseoli)
Figure 26. Bean fly pupae (left) and adult (right). Photos: W. Leedham
Adult bean flies (Figure 26) are tiny black Mungbean, cowpea, soybean and other
flies, 3 mm long (about one-quarter the legumes are attacked at seedling and
size of a common housefly), with one pair vegetative growth stages. Attacked
of transparent wings. Larvae are small, seedlings may be wilted or dead, and
white maggots with brown heads. Pupae leaves of older plants may be yellow and
are pale yellow, straw-coloured or light stunted. Damaged stems are thicker
brown, and can be seen sticking under the than normal and cracked lengthwise just
membranous epidermis, usually at the above the soil.
root–shoot junction.
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 33Twenty-eight spotted ladybird
(Henosepilachna vigintisexpunctata)
Figure 27. Twenty-eight spotted ladybird adult (left) and larva (right).
Photos: R. Martin
Adults are 5–8 mm long and are dull Larvae are elongate and elliptical
orange with black spots. The upper wing with moderately long legs and a
surface is covered in short downy hairs well-developed head and mandibles.
(Figure 27). This distinguishes plant- The body of the larva is covered with long,
feeding ladybird beetles from their branched processes (scoli) bearing spines
beneficial bug-feeding relatives. The eggs (Figure 27). Adults and larvae scrape away
are yellow, elongate and oval, and are leaf surface cells between the veins to
usually laid on the undersurface of leaves leave irregularly shaped holes or strips.
in batches of 5–40. They commonly feed on solanaceous
crops and weeds such as eggplant,
tomato, potato and Physalis angulata but
also feed on other crops.
34 MUNGBEAN PRODUCTION GUIDE I CAMBODIAINSECT PESTS
Cluster caterpillar
(Spodoptera litura)
Figure 28. Cluster caterpillar adult (left) and larva (right). Photos: R. Martin, W. Leedham
Moths of cluster caterpillar (Figure 28) are
up to 25 mm long. The eggs are laid in
clusters of up to 300 and are covered with
a mat of grey–brown hairs. Mature larvae
grow to up to 30 mm in length. They have
black triangles in a line on both sides of
the back, and the body narrows towards
the head. Larvae can almost completely
destroy leaves, and heavy infestations also
destroy buds and flowers.
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 35Legume web spinners
(Omiodes indicata, O. diemenalis)
Figure 29. Legume web spinner: adult O. diemenalis (left) and Omiodes indicata (centre); and
Omiodes larva (right). Photos: W. Leedham, R. Martin
Adult moths have a wingspan of The head is light brown. Larvae live
20–28 mm. O. indicata adult colour between two leaves spun together.
ranges from reddish yellow or In later stages they may spin several
orange–brown to dark grey with some leaves together, forming a mass of
lighter grey markings. O. diemenalis partially eaten leaves. They are most
adults are yellow with brown, broad active during the vegetative stage and
wavy bands and spots. Larvae are 15 mm are usually in insufficient numbers to
long, light to dark green on top and do economic damage.
yellowish green underneath; a single,
thin, greenish stripe runs lengthwise
down the middle of the back.
36 MUNGBEAN PRODUCTION GUIDE I CAMBODIAINSECT PESTS
Maruca podborer
(Maruca vitrata)
Figure 30. Maruca podborer adult (left) and larva (right). Photos: W. Leedham, R. Rien
Young larvae may be found together
among the flowers. Flowers may be
damaged and discoloured; flower-bud
shedding may occur and pod production
may be reduced. Pods have small,
darkened entry holes on the surface.
Leaves and pods are stuck together
by webbing and show signs of surface
feeding.
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 37Pea blue and gram blue butterflies
(Lampides boeticus and Euchrysops cnejus)
Figure 31. Pea blue (left) and gram blue (right) butterfly adults (above) and larvae (below).
Photos: R. Martin, R Rien
The wingspan is 24–34 mm. Males have a Caterpillars reach a length of 14–15 mm.
mainly blue-violet upper face of the wings Pupae reach a length of 9–10 mm. They
with brown edges, while the females are light grayish brown with medium-sized
have only a small amount of blue colour dark spots and a dark dorsal stripe. Larvae
in the centre of the wings. Both sexes of pea blue and gram blue butterflies
have a long, thin tail in the hindwings feed on flowers, seeds and pods of
and two black spots in the anal angle. many legume species. Crops attacked
Eggs are white with a greenish tinge and in Cambodia include cowpea, crotalaria,
have a disc-shaped form. They can reach long bean, mungbean, soybean and other
a diameter of 0.5 mm and are laid singly legume crop species.
on the flower buds of the host plants. Old
caterpillars are green or reddish brown,
with a dark dorsal stripe.
38 MUNGBEAN PRODUCTION GUIDE I CAMBODIAINSECT PESTS
Thrips
(Thripidae)
Figure 32. Bean flower thrip adults. Photos: R. Martin
Bean flower thrips (Megalurothrips usitatus; Deformed pods may be difficult to thresh,
Figure 32) are very small—about 1 mm resulting in further yield losses. There are
long—and barely visible to the naked eye. no thresholds for thrips at the seedling
Larvae are either yellow or white. Older stage. It is unlikely that this pest will
individuals are yellowish brown and move reduce mungbean yields except under
quickly. Bean flower thrips can infest extreme circumstances.
crops from the seedling stage, but are
more common at the bud initiation stage The spraying threshold for flowering
through to flowering. plants is 4–6 thrips per flower at flowering
and pod setting. Thrips are easily
Thrips damage the seedling growing point controlled with systemic insecticides, such
and embryonic leaves. However, damage as imidacloprid or thiamethoxam.
is not evident until the first trifoliate leaves
open. Damaged leaves can be severely
distorted and discoloured. Damage to
flowering plants can result in flower
abortion and pod distortion.
MUNGBEAN PRODUCTION GUIDE I CAMBODIA 39Whitefly (Bemisia tabaci) Figure 33. Whitefly. Photo: R. Gunning Adult Bemisia (Figure 33) are soft and whitish yellow when they first emerge from the nymph stage. Within a few hours, the wings become iridescent white as a result of a powdery wax. The body remains light yellow with a light dusting of wax. The female is 0.96 mm long, and the male is slightly smaller (0.82 mm). Tobacco whitefly transmits MYMV, which is a serious disease in mungbean (see ‘Mungbean yellow mosaic virus’, above). Seed treatment with imidacloprid is effective against B. tabaci. 40 MUNGBEAN PRODUCTION GUIDE I CAMBODIA
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